In an atom, there are 12 protons and 12 neutrons in the nucleus. Class 9

In an atom, there are 12 protons and 12 neutrons in the nucleus. Class 9

Question 1.

In an atom, there are 12 protons and 12 neutrons in the nucleus. Now, imagine that all the electrons are replaced with some hypothetical particles that have the same charge as electrons but are 500 times heavier. What effect will this replacement have on the atom’s: Class 9

(i) Atomic number

(ii) Atomic mass

(iii) Mass number

(iv) Overall charge

Answer:

(i) The atomic number is determined by the number of protons in the nucleus. Since the protons in the nucleus remain unchanged (we only replaced electrons, not protons), the atomic number will remain the same = 12.

(ii) Increases, because normally electrons have negligible mass, but replacing them with particles 500 times heavier adds significant extra mass to the atom.

(iii) Mass number = number of protons + number of neutrons. Both protons and neutrons remain unchanged (12 + 12 = 24). Electrons (or the hypothetical particles) are not included in the mass number calculation. Therefore, the mass number will remain unchanged = 24.

(iv) The hypothetical particles have the same charge as electrons (charge = -1 each). Since the number of hypothetical particles equals the original number of electrons (12), and they carry the same charge, the total negative charge remains -12. The total positive charge from the 12 protons remains +12. Therefore, the overall charge of the atom remains zero - the atom remains electrically neutral. The overall charge will not change.